Spray apparatus and method

ABSTRACT

Powder color change is accomplished easily and conveniently by providing a spray device having a channel or groove in its side and traversing its length in combination with one of a plurality of elongated, flexible powder feed tubes. The channel is formed from rigid material. One end of each of the feed tubes is connected to its cooperatively associated powder pump immersed in a powder reservoir. Each feed tube is adapted to be snapped into or out of the channel or groove of the spray device. The feed tube is retained in the channel in such a manner as to prevent harmful movement thereof with respect to the channel and other components of the device during the spraying operation. However, the feed tube is retained in the channel in such a manner as to permit the user to remove the tube from the channel without employing undue force or special tools. The feed tube selected to be snap fitted into the channel of the spray device dictates the color of the powder to be sprayed upon activation of the spray device. The system employing the spray device includes control means for switching from one powder reservoir to another powder reservoir upon removal of one feed tube from the spray device and insertion of another feed tube into the spray device.

nited States Patent [1 1 Probst et al.

[ 1 Dec. 11, 1973 SPRAY APPARATUS AND METHOD [75] Inventors: Richard 0.Probst; Kenneth R.

Pollard, both of Indianapolis; Frank R. Stockton, Brownsburg, all ofInd.

[73] Assignee: Ransburg Electro-Coating Corp.,

Indianapolis, Ind.

221 Filed: Nov. 18,1971 211 Appl. No.: 199,856

[52] U.S. Cl 239/1, 239/336, 239/426,

239/442, 239/526, 239/600, 222/567 [51] Int. Cl E0lb 1/00 [58] Field ofSearch 222/567, 568-575;

239/15, 317, 431, 442, 426,526, 419.3, DIG. 14, 531, 600, 305, 306

Primary Examiner-Lloyd L. King Att0rney--Merrill N. Johnson et a1.

[57] ABSTRACT Powder color change is accomplished easily andconveniently by providing a spray device having a channel or groove inits side and traversing its length in combination with one of aplurality of elongated, flexible powder feed tubes. The channel isformed from rigid material. One end of each of the feed tubes isconnected to its cooperatively associated powder pump immersed in apowder reservoir. Each feed tube is adapted to be snapped into or out ofthe channel or groove of the spray device. The feed tube is retained inthe channel in such a manner as to prevent harmful movement thereof withrespect to the channel and other components of the device during thespraying operation. However, the feed tube is retained in the channel insuch a manner as to permit the user to remove the tube from the channelwithout employing undue force or special tools. The feed tube selectedto be snap fitted into the channel of the spray device dictates thecolor of the powder to be sprayed upon activation of the spray device.

The system employing the spray device includes control means forswitching from one powder reservoir to another powder reservoir uponremoval of one feed tube from the spray device and insertion of anotherfeed tube into the spray device.

10 Claims, 5 Drawing Figures PAIENIEIlnsc 1 1 ms SHEET 30$ 3 SPRAYAPPARATUS AND METHOD The present invention relates to a spray deviceincluding means for and method of quickly and conveniently switching thedevice from ejecting or spraying coating material particles of onecolor, such as white, to ejecting or spraying coating material particlesof another color, such as black, without experiencing harmfulcontamination of the presently ejected coating material by coatingmaterial previously ejected or sprayed from the spray device.Preferably, the coating material is ejected from a spray deviceemploying electrostatic forces; the electrostatic forces assist indepositing particles of coating material on a surface to be coated, thesurface being maintained at a coating material attracting potential.

In several of the presently available powder devices, if the user of thespray device desires to switch or change from spraying coating materialsuch as powder of one color to spraying powder of another color, thespray device is disconnected from a powder pump immersed in powder andthe passageway of the feed tube from the pump to the spray device andthe spray device are purged of residue powder using compressed air,roughage, solvent flush and the like to prevent contamination of asubsequently sprayed powder with a previously sprayed powder. Then thepurged spray device is connected to another pump immersed in a reservoircontaining powder of the desired color and powder of the newly selectedcolor is sprayed from the spray device. Plastic powder conveyed througha plastic feed tube tends to experience frictional charging duringconveyence, due to, it is believed, random collisions with the side wallof the plastic feed tube. Charging of such plastic particles causesparticles to cling to the side wall of the feed tube making it difficultto properly clean the tube using, for example, compressed air. It shouldbe appreciated that the steps of disconnecting, purging and connectingthe spray device to yet another powder reservoir is a time consuming andexpensive method of switching from spraying powder of one color tospraying powder of another color.

Another suggested solution to the color change problem is to use adifferent spray device for each colored powder to be dispensed. Itshould be appreciated that such a solution is costly to the user, andrequires unusual amounts of space for equipment.

It is, therefore, a desideratum to provide means for r and method ofeasily and conveniently switching from spraying powder of one color tospraying powder of another color without purging the entire body of thespray device and its cooperatively associated powder tube and withoutexperiencing harmful contamination of subsequently sprayed powder withpowder previously sprayed from the spray device.

The invention facilitates color change by providing a spray devicehaving a channel or groove in its side and traversing its length incombination with one of a plurality of elongated, flexible feed tubes.The channel is made from a rigid material. One end of each of the feedtubes is connected to its cooperatively associated powder pump immersedin a powder reservoir. Each feed tube is adapted to be snapped into andout of the channel or groove of the spray'device. The feed tube isretained in the channel in such a manner as to prevent harmful movementthereof with respect to the channel and other components of the gunduring the spraying operation. However, the feed tube is retained insuch a manner as to permit the user to remove the feed tube from thechannel without employing undue force or special tools. The feed tubeselected by the user to be snap fitted into the channel of the spraydevice dictates the color of the powder to be sprayed upon activation ofthe spray device.

In the embodiment illustrated in the drawing, the spray device employsswirling gas (air) to assist in effecting a substantially uniformdistribution of the powder particles in the spray pattern ejected orsprayed from the device and to assist in providing the powder withsufficient momentum to be propelled to the vicinity of the article to becoated. When employing swirl air, the spray device includes anon-rotating powder distributing means having a sharp edge at which anelectrostatic field is concentrated. The field electrically charges thepower particles. While in the coating zone, the surface to be coated ismaintained at a particle attracting potential. The swirl air can beeliminated by using, at the front end of the spray device, a rotatingpowder distributing means, a flat-fan type spray nozzle and electrodeconfiguration of the type illustrated in U.S. Pat. No. 3,617,000, andthe like.

The appended drawings are intended to illustrate a powder spray deviceembodying the concepts of the present invention constructed to functionin the most advantageous mode presently devised for the practicalapplication of the principles involved in the hereinafter describedinvention. The powder spray device illustrated in several figures useselectrostatic forces to assist in depositing the powder particles on asurface to be coated. However, it is to be understood that the conceptsof the present invention can also be used with non-electrostatic powderspray devices.

In the drawings:

FIG. 1 is a diagrammatic illustration of an electrostatic powder systemembodying the concepts of the present invention;

FIG. 2 is a side view of the spray device illustrating an elongated,flexible tube snapped into and retained in position by the spray device;

FIG. 3 is a partial cross sectional view of the front end of the spraydevice taken across the lines 3-3 of FIG. 2;

FIG. 4 is a rear view of the spray device illustrated in FIG. 1; and

FIG. 5 is a schematic of a control panel for use with the powder spraydevice illustrated in FIG. 1.

Referring now to FIG. 1 of the drawing, an electrostatic powder spraysystem is illustrated by the reference numeral 10. The powder spraysystem 10 includes electrostatic spray device of gun 11, direct currentpower supply 12 connected to the gun, powder reservoirs l3, and controlpanel 14.

The structure of spray gun 11, which incorporates the concepts of theinvention, is shown in FIG. 2. The spray gun 11 includes barrel 15 andhandle 16. Handle 16, including grip portion 17, extends at an anglebelow barrel 15 to provide the user with means for gripping andmanipulating spray gun 11. Barrel 15 is fabricated from a suitableelectrically non-conductive material such as nylon, polyethylene and thelike. Handle 16 is fabricated from a suitable electrically conductivematerial such as aluminum, brass and the like.

Channel or groove 18 is formed in and traverses the length of the barrel15 and handle 16. Bore 19 is formed in and traverses the length ofbarrel l5 and bandle 16. An elongated, flexible feed tube 20 is shown asbeing snapped fitted into channel 18. Tabs 21 and 22 formed in barreland handle 16, respectively, cooperate with channel 18 to assist inretaining feed tube 20 therein. The diameter of channel 18 is slightlylarger than the outside diameter of tube 20. However, the opening ofchannel 18 through which feed tube 20 is inserted is slightly less inwidth than the outside diameter of the feed tube at tabs 21 and 22.

Elongated flexible feed tube 20 defines the passageway for conveyingpowder particles suspended in gas (air) between powder reservoir 13 andassembly 38 at the forward end of the gun l1. Snap fitting feed tube 20into channel 18 of the spray gun l1 suitably retains the tube in placewith respect to the other components of the spray gun and forms theelongated tube into a gradually curving passageway. The curvedpassageway of the feed tube is located in that portion of the barreladjacent the handle. Feed tube 20 is gradually curved in the gun so thatabrasive powder articles flowing through the curved portion of the tubehave less of an erosion effect on the curve of the passageway than suchparticles would have if the passageway was abruptly curved. This problemis largely avoided where a feed tube does not curve into the gripportion of the handle but extends rearwardly from the barrel along astraight line and passes out the rear of the gun over the hand of theuser. Attaching the feed tube in such a manner is unsatisfactory sincethe tube imposes a torque-like force on the spray gun which wouldfatigue the user and restrict the manipulability of the gun. As shown inMG. 1, a feed tube 20 projects downwardly from the base of handle 16where it imposes little restriction on the manipulability of the gun.

In the event of failure of feed tube 20 because of erosion of its wallsby powder particles or otherwise, the tube can be snapped out of channel18 and either the failure site removed by severing the tube behind suchsite and the tube reinserted into channel 18 or another tube can besubstituted therefor.

Assembly 38, mounted at the forward end of gun 11, includes bore 42axially aligned with the forward end 20a of feed tube 20. As shown inFIG. 3, the forward end 20a of feed tube 20 projects into and isretained in place by bore 42 by assembly 38. Powder suspended in air isconveyed through feed tube 20 into assembly 38 of spray device 11.Delivery of the powder particles to spray gun 11 is controlled by theuser displacing trigger 43 pivotally carried by gun 11. Depressingtrigger 43 actuates switch 28 which activates a solenoid valve (notshown) in power supply 12 causing powder to be withdrawn from powderreservoir 13 by venturi pump 36 and delivered through feed tube 20 toassembly 38. Powder supplied to assembly 38 is formed into a patternsuitable for application to the article to be coated.

Displacing trigger 43 also electrically connects the output terminal ofthe high voltage power supply 12 to edge 37 of assembly 38 through highvoltage cable 23, resistor 24, conductive plug 65 and conductive coating52 carried by non-rotating cylindrical means 49 of assembly 38. Powderejected from the assembly 38 is electrically charged by theelectrostatic field at edge 37 of assembly 38. Edge 37 is sharp so thatthe electrical field gradient at the edge is sufficiently high toprovide the powder with a high charge-to-mass ratio.

Assembly 38, shown in FIG. 3, includes head 45, out let passageway 46terminating in orifice 47, deflector 48 and non-rotating powderdistributing means 49. Head 45, deflector 48 and non-rotating means 49are fabricated from any suitable erosion resistant, dielectric materialsuch as nylon and the like in order to minimize wear sites andelectrical charging thereof during operation of the spray gun 11.Preferably, passageway 46 of head 45 has side walls as smooth as arepossible in order to minimize sites at which the entrained powder canaccumulate.

Powder baffle or deflector 48 is carried by rod 53. Rod 53 is integralwith spider-like means 54. The spider-like means 54 includes a pluralityof lengthwise apertures through which powder flows from feed tube 20toward baffle 48. Powder deflector 48 and orifice 47 cooperate so as toprovide annular opening 55 through which powder flows. The extent ofopening 55 may be varied by moving deflector 48 along rod 53. Afterselecting the desired location of deflector 48 along the length of rod53, the deflector is fixed in position by any suitable means such as byfrictional engagement of the deflector with the rod. The configurationof the periphery of deflector 48 may be round, ellipsoidal, or the likeso as to assist in providing a substantially uniform distribution ofpowder particles in annular opening 55. The radial extent of deflector48 should be greater than the radial extent of orifice 47. Orifice 47 isthe powder outlet orifice. The forward velocity of the particles ofpowder ejected from orifice 47 is decreased when the particles strikethe rear surface 56 of deflector 48. The powder is deflected about inall directions. Preferably, the axes of orifice 47 and deflector 48 arecoincident.

Powder particles are deflected toward interior surface 57 of cylindricalmeans 49 at a reduced velocity after striking the rear surface 56 of thedeflector 48. Jets of air are introduced along surface 57 substantiallytangentially to the direction of the flow of powder particles ejectedfrom orifice 47. The jets of air are introduced through a plurality ofapertures illustrated, in part, by apertures 58, 59, and 60 formed inthe side walls of head 45 to thereby assist in then effecting asubstantially uniform distribution of the powder over surface 57 ofcylindrical means 49. As many apertures as are necessary to achieve thedesired results may be formed in head 45. The jets of air intercept andswirl the powder over surface 57 in a substantially whirling,cyclone-type fashion. The powder moves in a substantially helicalfashion outwardly from the surface 57.

The swirl air flowing from apertures 58, 59, and 60 assists in providingthe powder particles with the momentum necessary to carry the powder tothe article to be coated. Further, the use of swirl air tends tominimize build-up powder particles on surface 57 during the sprayingoperation. If powder particles build up on surface 57, agglomerations ofparticles are formed and deposited on the articles. Such agglomerationsform a roughness in the coating that are visible after curing.Agglomerations of particles may also result in a multicolor coating.

Air is introduced to the apertures 58, 59, and 60 through bore 66 andair valve 67. Air valve 67 includes a finger actuated head 68, valvestem 69, an annular valve seat 70, and a nut 71 threadably retained onthe stem. The user of the gun can regulate the flow of swirl air toassembly 38 by appropriately adjusting nut 71.

The user may terminate the flow of swirl air by depressing stem 69.

Assembly 38 can be another configuration when a different spray patternis desired. For example, a flatfan spray nozzle including pin-likeelectrode can be substituted for non-rotating assembly 38. A suitableflat-fan spray nozzle and pin-like electrode combination for powderspraying is shown in U.S. Pat. No. 3,617,000.

Gun 11 includes bore 19 in the handle 16 and curved in barrel to formtubular passageway for electrical circuit means located within the gun.Bore 19 is formed of non-conductive material, has a sufficient wallthickness to withstand high direct current voltages, such as 40,000 upto 100,000 volts, which are applied to the gun. Bore l0 retains one endof high voltage cable 23 and resistor 24 having one end connected tocable 23. Resistor 24 is closely adjacent the forward end of the gun.Resistor 24 is a multi-megohm resistor having a typical valve of about160 inegohms. It is desirable to minimize the quantity of metallicconductive material associated with assembly 38 so as to minimize theeffective electrical capacity of the powder spray device. The advantagesof minimizing the effective capacity are disclosed in U.S. Pat. No.3,048,498. The safety features disclosed in that patent are desirablyincorporated in the spray gun 11.

The rear face 50 and outer surface 51 of means 49 are provided with asubstantially continuous conductive coating 52 having a highresistivity. A suitable material for coating 52 is described in US. Pat.No. 3,021,077. Conductive plug 65 and coating 52 connect resistor 24 toedge 37 of assembly 38. Assembly 38 also includes electricallyinsulative washer 25.

Powder spray gun 11, as illustrated in FIG. 1, ejects electricallycharged particles of powder toward articles 30 moved or displaced in thedirection of arrow 31 by conveyor 32. For the purpose of illustration,but not for the purpose of limitation, articles 30 are panels. Whilebeing coated with charged particles of powder, the articles 30 aremaintained at a powder particle attracting potential, such as groundpotential, by electrical connection to earth or ground 33 throughelectrically conductive hangers 34 of conveyor 32. Electrically chargedparticles of powder are propelled to the vicinity of articles 30 incoating zone 35 and are guided to the surface of the articles 30 byelectrostatic forces present in the coating zone. Coating zone 35 is thezone in which the powdered particles are deposited on the article(s)being coated.

High voltage direct current power supply 12, capable of supplying ano-load voltage of from about 40,000 up to 100,000 volts or more, isconnected in series with the spray gun 11 through electrical cable 23.The polarity of direct current voltage as supplied to gun 11 may beeither negative or positive, depending upon, among other things, thetype of powder sprayed. Some powder particles are more advantageouslycharged by a negative voltage than by a positive voltage and vice versa.

The powder reservoirs 13, as shown in FIG. 1, each contain a powder of adifferent color or type. The reservoirs 13 may number as few as two oras many as ten or more. Each reservoir includes means (not shown) forfluidizing the powder by passing flowing gas such as air through aforaminous sheet (not shown) located near the bottom of each reservoir.Gas flows through the foraminous sheet and is directed upwardly throughthe powder causing the powder to expand in volume and become fluidized.Powder of a suitable color or type is withdrawn from reservoir 13 bymeans of a venturi pump 36 immersed in the powder and delivered to gun I1 through an elongated flexible tube 20. Each reservoir includes aventuri pump 36.

Referring now to FIG. 5, one means of several possible means is shown toselect and control the flow of powder in the feed tube connected to thespray gun. One side of manually operated 3-way air valve 71, located incontrol panel 14, is connected to a compressed air source (not shown)via hose 72. The other side of valve 71 is connected to air manifold 73through hose 72a. When valve 71 is manually operated to an on" position(depressed), compressed air flows from valve 71 through manifold 73through hose 72b to spring biased pressure regulator 74. The pressure ofthe compressed air exiting regulator 74 is regulated by that regulator.The output of regulator 74 is connected to pressure gauge 75 throughhose 72c. Gauge 75 is used to display the air pressure of the airdelivered to the nozzle of the venturi pump. Compressed air also flowsfrom the output of regulator 74 through hose 72d to air piloted, springreturn 3-way valve 76. Activating valve 76 on causes compressed air toflow from the regulator 74 through valve 76 and hose 72e to a group 77of selector valves. Each of the selector valves of group 77 is an airpiloted spring return, 3-way valve. Air flowing through the activatedvalve of group 77 flows to a venturi pump.

Compressed air flowing through valve 76 also supplies air through hose72f for piloting reversing relay valve 78.

Compressed air from the compressed air source flow from air manifold 73through hose 72g to power supply 12 where such air flow is biased eitheron or off" by an electrical solenoid (not shown) internal of powersupply 12. The electrical solenoid is biased on by depressing trigger 43causing activation of switch 28 which in turn causes the solenoid to bebiased on and hence allowing compressed air to flow therethrough.Returning trigger 43 to its normal position biases switch 28 of as wellas biasing of the solenoid (not shown) connected thereto. Biasing thesolenoid in the power supply on, allows compressed air to passtherethrough and return to control panel 14 through hose 72h. Hose 72his connected to double air piloted 3-way valve 80. Biasing the solenoidof the power supply to off causes air to be exhausted to the atmospherethrough valve 80. However, biasing the solenoid on causes air from thecompressed air source to flow through valve 80 and hose 72i to selectorvalve group 81 composed of air piloted, spring return 3-way valves.Group 81 of 3-way valves is used to activate the pump valve cylinderassociated with each of the venturi pumps.

Air flowing from valve 80 through hose 72j is used to pilot air piloted,spring return 3-way valve 76. Air also flows from valve 80 through hose72k and restrictor valve 89 to the pilot of air piloted spring return3-way valve 82. Valve 89 allows air to free flow in one direction and byappropriate adjustment of valve 89 restricts the air flow in the reversedirection. Piloting 3-way valve 82 causes that valve to open. Openingvalve 82 causes compressed air from manifold 73 to flow through hose 72Land 72m to reversing relay valve 78. Valve 78 is a reversing relay whichprovides an output pressure that is the difference between a manuallyset, spring loaded pressure and a variable pneumatic signal. Reversingrelay valve 78 controls the flow of air through it dependent upon theair pressure supplied to its pilot by 3-way valve 76 through hose 72f.As the pressure of the pilot air supplied to reversing relay valve 78increases, the relay valve is activated so as to decrease the air flowallowed to pass through valve 78 from line 72m. Compressed air flowingthrough reversing relay valve 78 and hose 72n is supplied to selectorgroup 82 consisting of air piloted spring return 3-way valves. Airflowing through the activated valve of group 84 flows to the airinjector of a venturi pump.

Compressed air from manifold 73 flows through hose 720 to selector group85 consisting of air piloted spring return 3-way valves. Air flowingthrough the activated valve of the group 85 flows to the fluidizingchamber of the powder reservoir. There is one selector valve in eachgroup 77, 81, 84 and 85 for each reservoir. Two selector valves areshown in each group since, for clarity, two powder reservoirs have beenshown in the drawing. If ten powder reservoirs are incorporated into thesystem, then ten selector valves are included within each of the groupsof selector valves.

As shown in FIG. 5 there are four air lines 72p, 72q, 72r, and 72sconnected to each reservoir. The flow of air in these four lines iscontrolled by the four groups of valves 77, 81, 84 and 85; one group ofvalves for each line and each group contains one valve for each powderreservoir. The valves of groups 77, 81 and 84 are supplied air from thecompressed air source when the solenoid in the power supply is activatedon by switch 28. The valves of group 85, which control the flow of airto the fluidizing section of the reservoirs, received air from thecompressed air source through manifold 73 when valve 71 is activated.

When using the circuit of FIG. 5, the selection of powder to be sprayedfrom gun 11 is accomplished by manually activating either spring return4-way valve 87 or 87a each cooperatively associated with one valve ineach of the selector valve groups 77, 81, 84 and 85. The number of 4-wayspring return valves 87 and 87a is dictated by the number of differentpowders to be sprayed from gun 11. For convenience only two valves 87and 87a are shown in FIG. 5. Valve 87 is connected to manifold 73through hose 72!; valve 87a is serially connected to 4-way valve 87through hose 72v. All other 4-way valves likewise are serially connectedto valve 87. It is seen that each 4-way valve obtains its supply airfrom the preceding serially connected 4-way valve. The 4-way valve 87includes a suitable activating device 88 designed to hold a feed tube20. The feed tube is connected to the outlet of a venturi pump. When thetube is retained by device 88, the 4-way valve 87 or 87a associatedtherewith is biased off. When the tube is removed from activating device88 and inserted into channel 18 of the gun ll, 4-way valve 87 or 87acooperatively associated therewith is activated, thereby activating onevalve in each of the four groups 77, 81, 84 and 85 cooperativelyassociated therewith. The selected powder is withdrawn from thereservoir and supplied to gun 11. The powder feed begins when trigger 26is depressed. It should be understood other means for selecting thepowder to be sprayed from gun 11 can be substituted for the meansillustrated in FIG.

Swirl air for assembly 38 is supplied from manifold 13 through hose 72ato gun 11.

In operation, the user depresses trigger 43. As the trigger isdepressed, portion 27 of the trigger actuates switch 28 contained withinthe gun 11. Conductors (not shown) from electrical switch 28 run throughthe grip portion of the handle and are connected to the solenoid valve(not shown) internal of the power supply 12 in such a manner as to turnon the voltage supply and withdraw powder from the desired powerreservoir. Air flowing through venturi pump 36 thus entrains the solidparticles of coating material and directs the entrained powder into feedtube 20. Since the entire passageway of the feed tube 20 from theventuri pump 36 into the assembly 38 has a uniform cross-section andcurves gradually in the barrel, the coating material particles flow toassembly 38 in a substantially stable sus pension. The operator mayeasily change the color of the powder being ejected by removing one feedtube and inserting another feed tube by snapping it into channel 18.

Powder, as that term is used herein, means and includes thermoplasticdry powders such as polyester, polyvinyl chloride, polypropylene,polyethylene, nylon, cellulose acetate butyrate; thermosetting resinssuch as epoxies, polyesters, acrylics; other powder such as starch,talc, vitreous enamel; and the like. Preferably, the individual powderparticles are receptive to acquiring and retaining an electric chargefor a predetermined length of time or are capable of being suitablytreated so as to accept and retain an electric charge for apredetermined length of time. The powder particle shape and size shouldbe such as to permit proper distribution on the surface to be coated sothat the fused coating is of good structural strength and appearance.The melt viscosity and surface tension of the particles of powder shouldbe such as to provide a film that adheres to the surface to protect anddecorate that surface.

Generally, powders suitable for spraying are prepared by grinding bulkmaterial, usually at a low temperature. Powder having a particle size inthe order of about 20 to about 250 microns is preferred forelectrostatic powder spraying, however, the powder may be coarser orfiner, depending on the particular material and application thereof.

While we have shown and described the preferred embodiment of ourinvention, it is to be understood that it is capable of manymodifications. Changes, therefore, in the construction and arrangementmay be made without departing from the spirit and scope of the inventionas disclosed in the following claims.

We claim:

1. A powder spray device for easily and conveniently accomplishingswitching from spraying one type of coating material to spraying coatingmaterial of another type without harmfully contaminating thesubsequently sprayed coating material with previously sprayed coatingmaterial, the spray device including means forming a barrel, and ahandle and carrying a spray forming nozzle, a channel provided in theside of the barrel traversing the length of the barrel and communicatingwith the spray-forming nozzle, and an elongated feed tube adapted tohave one end connected to a powder reservoir and to fit in the channel,the means being shaped to retain the feed tube in the channel and insealed engagement with the spray-forming nozzle so as to deliver powderto the nozzle and to prevent harmful movement thereof during thespraying operation.

2. The spray device of claim 1, wherein the channel is curved within thebarrel and handle of the spray device.

3. The spray device of claim 2, wherein the forward end of the feed tubeis retained at the forward end of the spray device by the spray-formingnozzle and at the handle by means of the elongated feed tube adapted tocooperate with the handle.

4. The spray device of claim 1 in combination with means for selectingone coating material reservoir from several coating reservoirs fromwhich coating material is withdrawn and supplied to the feed tube.

5. The combination of claim 4, wherein the means for selecting thecoating material includes a plurality of feed tubes, a different feedtube cooperatively associated with each reservoir and means forretaining unused feed tubes to deactivate the coating materialreservoirs cooperatively associated with the unused feed tubes, removingthe feed tube from the retaining means activating the coating materialreservoir cooperatively associated therewith so that coating materialcan be withdrawn from that reservoir and delivered to the gun.

6. A powder spray gun for easily and conveniently accomplishingswitching from spraying powder of one color to spraying powder ofanother color without harmfully contaminating the subsequently sprayedpowder with previously spray powder, the spray gun comprising a barreland a handle projecting at an angle from the barrel, a channel providedin the side of the barrel and handle and traversing the length of each,a spray-forming nozzle carried at the front of the barrel and anelongated feed tube adapted to have one end connected to a powderreservoir, the feed tube capable of being inserted into the channel andretained in the channel at the front of the gun by the spraying nozzleand at the rear of the gun by means on the tube cooperating with thehandle so as to prevent harmful movement thereof, the elongated tubebeing in communica tion with the spray-forming nozzle when retained inthe channel.

7. The spray gun of claim 8, wherein the gun includes tab means in thebarrel and the handle for retaining the tube in the channel.

8. The spray device of claim 6, in combination with means for selectingone powder from several powders and for supplying the selected powder tothe feed tube in the channel of the spray gun.

9. The combination of claim 8, wherein the means for selecting thepowder includes at least two feed tubes and two powder reservoirs, andmeans for retaining the unused feed tube to deactivate the reservoirconnected to the unused feed tube, removing a feed tube from theretaining means activating the reservoir connected thereto so thatpowder can be withdrawn from that reservoir and delivered to the gun.

10. In a method for easily and conveniently accomplishing switching fromspraying powder of one type to powder of another type without harmfullycontaminating the subsequently sprayed powder with previously sprayedpowder, the steps including providing a spray device having a barrel,carrying spray-forming nozzle, and including a channel traversing thelength of the barrel and communicating with a spray-forming nozzle,inserting and removing feed tubes having one end connected to powderreservoirs into the channel and in sealed communication with thespray-forming nozzle with a snap-like action, and spraying coatingmaterial withdrawn from the reservoir from the spray-forming nozzle ofthe device.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No.3,777,981 D d December ll, 11.973

Inventor(s) Richard O Probst: et 1 It is certified that error appears inthe above-identified patent and that said Letters Patent are herebycorrected as shown below:

on the cover sheet under item [75] "Kenneth R. Pollard" should readKenneth E. Pollard Column L line 55, after "build-up" insert of Column5', line is, "l0 should read l9 Column 6, line 3h, ""flow" should readflows Column 7; line ll, "82" should read 8h line ll before "manifold"insert air Column 9, line 13 after 'Ycoating" insert material Column 10,line 1, "spraying should read sprayforming I line 7, "8" should read 6Signed and sealed this 30th day or April 197E.

(SEAL) Attest:

EDWARD I LFLETCIDSRJR. C. MARSHALL DAM Attesting Officer Commissioner ofPatents FORM FO-I SO 0-69) I uscoMM-oc 60376-P69 r v Q GQVERNMENTQRIHTING O FFICE: I919 0-'3B6-33"

1. A powder spray device for easily and conveniently accomplishingswitching from spraying one type of coating material to spraying coatingmaterial of another type without harmfully contaminating thesubsequently sprayed coating material with previously sprayed coatingmaterial, the spray device including means forming a barrel, and ahandle and carrying a spray forming nozzle, a channel provided in theside of the barrel traversing the length of the barrel and communicatingwith the spray-forming nozzle, and an elongated feed tube adapted tohave one end connected to a powder reservoir and to fit in the channel,the means being shaped to retain the feed tube in the channel and insealed engagement with the spray-forming nozzle so as to deliver powderto the nozzle and to prevent harmful movement thereof during thespraying operation.
 2. The spray device of claim 1, wherein the channelis curved within the barrel and handle of the spray device.
 3. The spraydevice of claim 2, wherein the forward end of the feed tube is retainedat the forward end of the spray device by the spray-forming nozzle andat the handle by means of the elongated feed tube adapted to cooperatewith the handle.
 4. The spray device of claim 1 in combination withmeans for selecting one coating material reservoir from several coatingreservoirs from which coating material is withdrawn and supplied to thefeed tube.
 5. The combination of claim 4, wherein the means forselecting the coating material includes a plurality of feed tubes, adifferent feed tube cooperatively associated with each reservoir andmeans for retaining unused feed tubes to deactivate the coating materialreservoirs cooperatively associated with the unused feed tubes, removingthe feed tube from the retaining means activating the coating materialreservoir cooperatively associated therewith so that coating materialcan be withdrawn from that reservoir and delivered to the gun.
 6. Apowder spray gun for easily and conveniently accomplishing switchingfrom spraying powder of one color to spraying powder of another colorwithout harmfully contaminating the subsequently sprayed powder withpreviously spray powder, the spray gun comprising a barrel and a handleprojecting at an angle from the barrel, a channel provided in the sideof the barrel and handle and traversing the length of each, aspray-forming nozzle carried at the front of the barrel and an elongatedfeed tube adapted to have one end connected to a powder reservoir, thefeed tube capable of being inserted into the channel and retained in thechannel at the front of the gun by the spraying nozzle and at the rearof the gun by means on the tube cooperating with the handle so as toprevent harmful movement thereof, the elongated tube being incommunication with the spray-forming nozzle when retained in thechannel.
 7. The spray gun of claim 8, wherein the gun includes tab meansin the barrel and the handle for retaining the tube in the channel. 8.The spray device of claim 6, in combination with means for selecting onepowder from several powders and for supplying the selected powder to thefeed tube in the channel of the spray gun.
 9. The combination of claim8, wherein the means for selecting the powder includes at least two feedtubes and two powder reservoirs, and means for retaining the unused feedtube to deactivate the reservoir connected to the unused feed tube,removing a feed tube from the retaining means activating the reservoirconnected thereto so that powder can be withdrawn from that reservoirand delivered to the gun.
 10. In a method for easily and convenientlyaccomplishing switching from spraying powder of one type to powder ofanother type without harmfully contaminating the subsequently sprayedpowder with previously sprayed powder, the steps including providing aspray device having a barrel, carrying spray-forming nozzle, andincluding a channel traversing the length of the barrel andcommunicating with a spray-forming nozzle, inserting and removing feedtubes having one end connected to powder reservoirs into the channel andin sealed communication with the spray-forming nozzle with a snap-likeaction, and spraying coating material withdrawn from the reservoir fromthe spray-forming nozzle of the device.